We are having difficulty mainaining support for Clang at the moment because the way that template specialization is handled changes with every release and we have to add/change a bunch of #ifdef statements accordingly. So far we have not seen any performance advantage in using Clang so we have not been pursuing it for the moment. We will have another go at a Clang port for the next release of OpenFOAM.

Currently there is no performance advantage but this is a young compiler which is undergoing intensive development and at some point the optimization may be better than the competition and we intend to support Clang when it is more stable.

Note that there are already some advantages in using Clang, in particular the error messages from templating are more comprehensible than from gcc, icc etc.

The license choice is not an advantage over gcc for OpenFOAM which we release GPLv3 anyway.